When a person sits on a rear seat of a vehicle, the vehicle body tilts backward. Also, when a load or the like is loaded on the rear seat, a rear trunk, or the like, the vehicle body tilts backward. When the vehicle is accelerated, the vehicle body tilts backward; when it is decelerated, the vehicle body tilts forward. Here, “tilts” refers to tilting due to rotation of the vehicle body about an axis of a wheel of the vehicle.
When the vehicle body tilts forward or backward in this way, a light distribution of a headlight changes in an up-down direction. Here, “up” refers to a direction toward the sky, and “down” refers to a direction toward the ground. Thus, “up-down direction” refers to a direction perpendicular to the ground. “Light distribution” refers to a spatial distribution of light emitted from a light source. Here, it refers to an area onto which the headlight projects light and the intensity of the light. “Headlight” refers to an illuminating device that is mounted on a transportation machine or the like and used to improve visibility for an operator. It is also referred to as a headlamp or headlight.
The change of the light distribution of the headlight in the up-down direction prevents the vehicle from providing an optimum light distribution, resulting in a problem of reduction in visibility for the driver. It also causes a problem of dazzling an oncoming vehicle. “Dazzling” refers to confusing a person's vision. Here, it indicates that light from the headlight enters the eyes of the driver of the oncoming vehicle and interferes with driving.
As a countermeasure against this, Patent Reference 1 discloses a vehicle lamp in which the direction of a beam projected by a lamp unit is changed. The lamp unit is supported in a suspending state on a bracket. The bracket is supported on a lamp body to be movable vertically and horizontally. The lamp unit includes a reflector, a discharge lamp, a projection lens, and a shade. A rotating force is transmitted from an output shaft to the lamp unit, so that the direction of a beam projected by the lamp unit is changed.